NEW ORLEANS - Two men died and 61 other people were injured Thursday in a pre-dawn pileup involving about 40 cars, vans and other vehicles on a busy interstate that crosses New Orleans, closing the route for hours both ways, police said.

Drivers said they drove into thick smoke or fog that abruptly limited visibility on westbound lanes of Interstate 10 heading across eastern New Orleans. Those who came upon the scene said they heard injured motorists pleading for assistance.

"You just hear all kinds of calls and people screaming for help," tow truck driver Wesley Ratcliff told local broadcaster WWL-TV. In 13 years responding to wrecks, he added, "this is the worst I've ever seen it."

Officer Garry Flot, a police spokesman, would not talk about possible causes, including whether those may have included smoke or fog.

The highway's westbound lanes were still closed late Thursday afternoon as the investigation continued, but eastbound lanes were reopened, letting commuters head home at rush hour.

The highway is heavily trafficked, a major corridor for thousands of commuters who enter New Orleans each day from its eastern suburbs and the Mississippi Gulf Coast. Those driving the route at the time of the wrecks said they suddenly found themselves in utter darkness, unable to see the lights of cars ahead.

"I thought it was fog; my husband thought it was smoke," Stacie Williams told WWL-TV (http://bit.ly/sLHWVx ). "Cars were driving in front of us and before you know it, it seemed as if they had dropped off the face of the Earth."

Seven people were taken to south Louisiana's top trauma center, where several were in critical condition, said Marvin McGraw, spokesman for the Interim LSU Public Hospital.

Flot said 25 people were taken to hospitals with injuries ranging from minor to critical. He said they included a 62nd injured person - a firefighter whose face was cut while working at the scene. Flot said 37 others refused treatment for minor injuries.

The police spokesman wouldn't say whether police believe smoke or fog contributed to the wreck, noting the investigation is ongoing.

He said the dead were a pickup truck driver and a 54-year-old passenger in another pickup, both from Louisiana. He wouldn't say whether their pickup trucks were among the first vehicles to crash or part of the pileup that followed.

Cars, tractor-trailers, vans and other vehicles collided on lanes approaching the city's business district. Eastbound lanes were closed to let emergency vehicles get in, and traffic was detoured off the highway through morning rush hour and well into the afternoon.

Interstate 10 stretches from Florida to California and is a major corridor for commercial truck traffic.